The invention relates to an electric lamp comprising:
an envelope with a neck and a light source;
a lamp cap provided with contacts, which lamp cap is fixed around a free end portion of the neck; and
current conductors which are passed from the light source through the free end portion of the neck and are electrically connected to the contacts of the lamp cap.
Such an electric lamp is known from EP-0 758 486. The known lamp is a reflector lamp with a light emission window, the envelope being internally partly reflectorized. The light source is placed in the known lamp in a lamp vessel which is mechanically secured in a plate. The plate and the lamp. vessel are fixed in the neck of the envelope by means of cement. The current conductors passed through the free end portion of the neck issue into the lamp cap, which is hollow. The lamp cap has a screwthread-type contact around an axis and a central electrical contact situated on the axis. The current conductors of the light source are flexible and are guided towards the contacts in the hollow lamp cap, for example in that they are bent, and are fixed to these contacts by means of welding or soldering. It is a disadvantage of the known lamp that achieving the electrical contact between the current conductors of the light source and the contacts of the lamp cap by means of welding or soldering involves a comparatively cumbersome and difficult process. This is rendered more difficult in part by the size of the light source, which leaves comparatively little space for achieving the contact. In addition, welding/soldering is a process which is comparatively hard on the environment. Undesirable bending of the flexible current conductors may arise as a result of external forces, such as shocks and impacts, because the current conductors in the hollow lamp cap are not screened from one another in the known lamp. As a result, the known lamp has the additional disadvantage that there is a comparatively high risk of short-circuits caused by the current conductors approaching one another too closely or even touching one another owing to their undesired bending.
It is an object of the invention to provide an electric lamp of the kind described in the opening paragraph which has a comparatively safe construction and which renders possible a simple assembly of the lamp.
According to the invention, this object is achieved in that an insulator body provided with connection conductors is accommodated in the lamp cap for the electrical connection of the current conductors to the contacts of the lamp cap, at least one of the connection conductors comprises an end portion, which end portion comprises a cylindrical portion of a given shape, which defines a cylinder axis, said cylindrical portion comprising:
a slit extending parallel to the cylinder axis and bounded by two cylinder edges extending parallel to the cylinder axis and spaced apart from one another by a slit spacing S for retaining the current conductor, and
an opening which is provided in the cylindrical portion, which lies substantially opposite the slit, and through which the current conductor can be passed.
The connection conductors are passed through the insulator body through respective channels. The channels are separate from one another. The current conductors and the connection conductors electrically connected thereto through the insulator body are thus mechanically screened off from one another. This renders the lamp comparatively safe because the risk of short-circuits caused by the current conductors touching each other is reduced. The channels in the insulator body each comprise a recess. The end portion of the connection conductor extends into this recess, while a further end portion of the connection conductor is electrically connected to the contact of the lamp cap, for example by means of a resilient contact or, for example, in that the further end portion is clamped in between the insulator body and the lamp cap. The resilient contact has the advantage that the electrical connection between the connection conductor and the contact on the lamp cap can be achieved without welding or soldering. This simplifies the lamp assembling process and is less hard on the environment. The current conductor is inserted as far as possible into the recess, with the result that the current conductor also extends through the opening and the slit of the cylindrical portion of the connection conductor, thus making electrical contact therewith. The electrical contact between the current conductor and the contact on the lamp cap via the connection conductor is thus achieved in a comparatively simple manner. This further simplifies the lamp assembling process.
The connection conductor with its cylindrical portion has a simple shape which can be realized in a comparatively simple and inexpensive manner, for example by stamping out of the opening and deformation of metal plating, whereby the cylindrical portion is formed and the cylinder edges are brought to a slit distance S from one another. Usually, the opening is elongate and has a minimum cross-section D which is greater than the slit width S. It is also true here that it is desirable for electrical contacting that the slit width S should be smaller than a smallest diameter of the current conductor. Such a current conductor allows of comparatively wide tolerances in dimensioning and mutual interspacing of the current conductors, so that a reliable electrical contacting can be realized in a simple manner.
In an embodiment, the end portion is a clamping/scraping contact. An inadvertent retraction from the slit of the current conductor passed through the slit is counteracted by the clamping/scraping contact, for example a contact which has a clamping, hooking, and/or abrasive effect on the current conductor introduced therein. The risk of breaking of the electrical contact with the contact on the lamp cap is reduced thereby.
In a further embodiment, the cylinder edge comprises a tag which faces away from the opening. A cylinder edge having such a shape facilitates the insertion of the current conductor into the slit. In addition, a cylinder edge having such a shape provides an improved electrical contacting with the current conductor passed through the slit. If the tag has a hooking effect, an improved hooking action on a current conductor passed through the slit is obtained. The removal from the slit of this current conductor is rendered more difficult thereby, and the risk of breaking of the electrical contact with the contact on the lamp cap is further reduced.
In a favorable embodiment of the electric lamp, the cylindrical portion is resilient. A permanent, satisfactory electrical contacting between the current conductor and the connection conductor is realized in that the cylinder edges bear on the current conductor under spring force. A yet further improved clamping, scraping, and/or hooking action of the cylinder on a current conductor passed through the slit is obtained thereby. In addition, it is even more difficult to remove the current conductor from the slit, and the risk of breaking of the electrical contacting with the contact on the lamp cap is further reduced. The resilient cylindrical portion may be obtained in a simple manner in that the cylindrical portion is manufactured from materials suitable for the purpose, for example from spring steel, and through suitable dimensions of the cylindrical portion. The dimensions of the cylindrical portion suitable for adjusting the spring force with which the cylinder edges bear on the current conductor are, inter alia, the cylinder length Lc, the thickness of the material from which the cylinder is manufactured, the dimension of the opening in axial direction Lo, and the maximum dimension H of the cylindrical portion in relation to the width Bc of the cylindrical portion. It is favorable when H is at most 0.25xc3x97Bc. At a higher H/Bc ratio, there is an increased risk of the cylindrical portion having an insufficient resilient effect, so that the cylinder edges bear on the current conductor with a too small spring force.
In a further embodiment, the envelope is internally reflectorized between the neck and the light emission window. The reflector body thus formed has a concave, beam-forming portion with an optical center and is present between the neck and the light emission window. The light source is arranged axially in the optical center. The light generated by the light source can be formed into a beam and directed in a simple manner by means of the reflector body in the reflector lamp thus obtained.
In an embodiment, the insulator body is made of synthetic resin, porcelain, glass, or ceramic material. It is favorable for the use of the lamp at comparatively high temperatures if the insulator body is made of porcelain, glass, or a ceramic material because of the good temperature resistance of these materials. If the lamp is to be operated at comparatively low temperatures, the insulator body is preferably made of a synthetic resin, because an insulator body of synthetic resin can be manufactured in a comparatively simple and inexpensive manner.
It is favorable for achieving a reproducible position of the insulator body in the lamp cap when the insulator body is provided with a recess which cooperates with the lamp cap. The insulator body is retained in the lamp cap in that the lamp cap is indented into said recess. The insulator body and the lamp cap are locked against mutual rotation about the axis thereby. Such a rotation may occur as a result of torques, for example during screwing of the lamp into or from a luminaire. In addition, the assembling process of the electric lamp is further simplified thereby because an additional position definition of the insulator body in the lamp cap with respect to the light source is avoided. This also reduces the risk of short-circuits between the current conductors in the lamp cap owing to a rotation of the insulator body with respect to the lamp cap. Since the insulator body and the lamp cap are locked against mutual rotation, a permanent, secure clamping-in of the further end portion between the insulator part and the lamp cap is realized at the same time. The risk of breaking of an electrical contact between the lamp cap and the connection conductor is thus reduced.
In the known lamp, the light source is aligned and fixed in the neck of the envelope by means of cement, for example lamp cement. It is disadvantageous, however, for a reflector lamp that cement evolves volatile ingredients which impair the reflecting power of the reflector body, also after curing of the cement. In the lamp according to the invention, the use of cement for this purpose is avoided in that a reproducible fixed position of the insulator body in the lamp cap is achieved in that the insulator body is accommodated in the lamp cap with narrow fit. The insulator body may have, for example, a screwthread-type surface for this purpose, in which case the insulator body can be turned into the lamp cap, which has a screwthread-type contact. The fact that the insulator body is fixed in the lamp cap renders it possible to secure the light source aligned in the reflector lamp in cooperation with the clamping/fixing end portion. A yet further simplification in the lamp assembling process is also achieved thereby.
In a further favorable embodiment of the electric lamp, at least one connection conductor at the same time comprises one contact of the lamp cap. Since a separate welding or soldering operation for electrically connecting the connection conductor to the contact of the lamp cap is avoided, the lamp assembling process is yet further simplified, and the environment is further spared. In addition, a yet more reliable electrical contact is achieved in this way.
The light source may be an incandescent body, possibly in an atmosphere comprising halogen, or a discharge path between electrodes in an ionizable medium, for example metal halides in rare gas, possible with mercury. The light source may be provided in a lamp vessel made of glass, for example of hard glass or glass having an SiO2 content of at least 95% by weight such as, for example, quartz glass, or of monocrystalline or polycrystalline material such as, for example, translucent aluminum oxide. The lamp vessel may be surrounded by an outer bulb.
The reflector lamp may be provided with a light-transmitting cover which is fastened to the reflector body and which closes off the light emission window.